Flame retardant polycarbonate compositions, methods of manufacture thereof and articles comprising the same

ABSTRACT

Disclosed herein is a flame retardant composition comprising 10 to 90 weight percent of a linear polycarbonate; 5 to 50 weight percent of a polysiloxane-polycarbonate copolymer; where the polysiloxane-polycarbonate copolymer comprises 10 weight percent or more of polysiloxane and where the molecular weight of the polysiloxane is 30,000 grams per mole or greater; and 1 to 20 weight percent of a phosphazene compound; where all weight percents are based on the total weight of the composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/651,481 filed on May 24, 2012, and to U.S. Provisional Application No. 61/651,487, filed on May 24, 2013, the entire contents of which are hereby incorporated by reference.

BACKGROUND

This disclosure relates to flame retardant polycarbonate compositions, methods of manufacture thereof and to articles comprising the same.

In electronic and electrical devices such as notebook personal computers, e-books, and tablet personal computers, metallic body panels are being replaced by materials that are lighter in weight and offer a robust combination of mechanical properties. These lighter materials result in weight savings, cost savings, and enable the manufacture of complex designs. While these lighter materials can be used to manufacture panels having thinner cross-sectional thicknesses, it is desirable to improve the ductility of the material to prevent cracking. It is also desirable to improve the flame retardancy of the material to reduce fire related hazards.

SUMMARY

Disclosed herein is a flame retardant composition comprising 10 to 90 weight percent of a linear polycarbonate; 5 to 50 weight percent of a polysiloxane-polycarbonate copolymer; where the polysiloxane-polycarbonate copolymer comprises 10 weight percent or more of polysiloxane and where the molecular weight of the polysiloxane is 30,000 grams per mole or greater; and 1 to 20 weight percent of a phosphazene compound; where all weight percents are based on the total weight of the composition.

Disclosed herein too is a method comprising blending 10 to 90 weight percent of a linear polycarbonate; 5 to 50 weight percent of a polysiloxane-polycarbonate copolymer; where the polysiloxane-polycarbonate copolymer comprises 10 weight percent or more of polysiloxane and where the molecular weight of the polysiloxane is 30,000 grams per mole or greater; and 1 to 20 weight percent of a phosphazene compound; where all weight percents are based on the total weight of the composition; to form a flame retardant composition; were all weight percents are based on the total weight of the composition.

DETAILED DESCRIPTION

Disclosed herein is a flame retardant polycarbonate composition that displays a suitable combination of ductility as well as super thin wall flame retardancy. The flame retardant polycarbonate composition is opaque in the visible wavelength region of the electromagnetic spectrum.

Disclosed herein too is a method of manufacturing an opaque flame retardant polycarbonate composition. The flame retardant polycarbonate composition comprises a polycarbonate composition, a phosphazene oligomer, a polysiloxane-polycarbonate copolymer, and/or a mineral filler, and an anti-drip agent. The flame retardant polycarbonate composition displays an advantageous combination of properties that renders it useful in electronics goods such as notebook personal computers, e-books, tablet personal computers, and the like.

In the embodiment, the polycarbonate composition comprises a polycarbonate homopolymer and a polysiloxane-polycarbonate copolymer (also termed a polysiloxane-carbonate copolymer). The polycarbonate used as a homopolymer may be a linear polymer, a branched polymer, or a combination thereof.

The term “polycarbonate composition”, “polycarbonate” and “polycarbonate resin” mean compositions having repeating structural carbonate units of the formula (1):

wherein at least 60 percent of the total number of R¹ groups may contain aromatic organic groups and the balance thereof are aliphatic or alicyclic, or aromatic groups. R¹ in the carbonate units of formula (1) may be a C₆-C₃₆ aromatic group wherein at least one moiety is aromatic. Each R¹ may be an aromatic organic group, for example, a group of the formula (2):

-A¹-Y¹-A²-  (2)

wherein each of the A¹ and A² is a monocyclic divalent aryl group and Y¹ is a bridging group having one or two atoms that separate A¹ and A². For example, one atom may separate A¹ from A², with illustrative examples of these groups including —O—, —S—, —S(O)—, —S(O)₂)—, —C(O)—, methylene, cyclohexyl-methylene, 2-[2.2.1]-bicycloheptylidene, ethylidene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, and adamantylidene. The bridging group of Y¹ may be a hydrocarbon group or a saturated hydrocarbon group such as methylene, cyclohexylidene, or isopropylidene.

The polycarbonates may be produced from dihydroxy compounds having the formula HO—R¹—OH, wherein R′ is defined as above for formula (1). The formula HO—R¹—OH includes bisphenol compounds of the formula (3):

HO-A¹-Y¹-A²-OH  (3)

wherein Y¹, A¹, and A² are as described above. For example, one atom may separate A¹ and A². Each R¹ may include bisphenol compounds of the general formula (4):

where X_(a) is a bridging group connecting the two hydroxy-substituted aromatic groups, where the bridging group and the hydroxy substituent of each C₆ arylene group are disposed ortho, meta, or para (specifically para) to each other on the C₆ arylene group. For example, the bridging group X_(a) may be single bond, —O—, —S—, —C(O)—, or a C₁₋₁₈ organic group. The C₁₋₁₈ organic bridging group may be cyclic or acyclic, aromatic or non-aromatic, and can further comprise heteroatoms such as halogens, oxygen, nitrogen, sulfur, silicon, or phosphorous. The C₁₋₁₈ organic group can be disposed such that the C₆ arylene groups connected thereto are each connected to a common alkylidene carbon or to different carbons of the C₁₋₁₈ organic bridging group. R^(a) and R^(b) may each represent a halogen, C₁₋₁₂ alkyl group, or a combination thereof. For example, R^(a) and R^(b) may each be a C₁₋₃ alkyl group, specifically methyl, disposed meta to the hydroxy group on each arylene group. The designation (e) is 0 or 1. The numbers p and q are each independently integers of 0 to 4. It will be understood that when p or q is less than 4, any available carbon valences are filled by hydrogen.

X_(a) may be substituted or unsubstituted C₃₋₁₈ cycloalkylidene, a C₁₋₂₅ alkylidene of formula —C(R^(c))(R^(d))— wherein R^(c) and R^(d) are each independently hydrogen, C₁₋₁₂ alkyl, C₁₋₁₂ cycloalkyl, C₇₋₁₂ arylalkyl, C₁₋₁₂ heteroalkyl, or cyclic C₇₋₁₂ heteroarylalkyl, or a group of the formula —C(═R^(c))— wherein R^(e) is a divalent C₁₋₁₂ hydrocarbon group. This may include methylene, cyclohexylmethylene, ethylidene, neopentylidene, isopropylidene, 2-[2.2.1]-bicycloheptylidene, cyclohexylidene, cyclopentylidene, cyclododecylidene, and adamantylidene. A specific example wherein X_(a) is a substituted cycloalkylidene is the cyclohexylidene-bridged, alkyl-substituted bisphenol of formula (5):

wherein R^(a′) and R^(b′) are each independently C₁₋₁₂ alkyl, R^(g) is C₁₋₁₂ alkyl or halogen, r and s are each independently 1 to 4, and t is 0 to 10. R^(a′) and R^(b′) may be disposed meta to the cyclohexylidene bridging group. The substituents R^(a′), R^(b′) and R^(g) may, when comprising an appropriate number of carbon atoms, be straight chain, cyclic, bicyclic, branched, saturated, or unsaturated. For example, R^(g) may be each independently C₁₋₄ alkyl, R^(g) is C₁₋₄ alkyl, r and s are each 1, and t is 0 to 5. In another example, R^(a′), R^(b′) and R^(g) may each be methyl, r and s are each 1, and t is 0 or 3. The cyclohexylidene-bridged bisphenol can be the reaction product of two moles of o-cresol with one mole of cyclohexanone. In another example, the cyclohexylidene-bridged bisphenol may be the reaction product of two moles of a cresol with one mole of a hydrogenated isophorone (e.g., 1,1,3-trimethyl-3-cyclohexane-5-one). Such cyclohexane-containing bisphenols, for example the reaction product of two moles of a phenol with one mole of a hydrogenated isophorone, are useful for making polycarbonate polymers with high glass transition temperatures and high heat distortion temperatures. Cyclohexyl bisphenol-containing polycarbonates, or a combination comprising at least one of the foregoing with other bisphenol polycarbonates, are supplied by Bayer Co. under the APEC® trade name.

In an embodiment, X_(a) is a C₁₋₁₈ alkylene group, a C₃₋₁₈ cycloalkylene group, a fused C₆₋₁₈ cycloalkylene group, or a group of the formula —B₁—W—B₂— wherein B₁ and B₂ are the same or different C₁₋₆alkylene group and W is a C₃₋₁₂ cycloalkylidene group or a C₆₋₁₆ arylene group.

In another example, X_(a) may be a substituted C₃₋₁₈ cycloalkylidene of the formula (6):

wherein R^(r), R^(p), R^(q), and R^(t) are independently hydrogen, halogen, oxygen, or C₁₋₁₂ organic groups; I is a direct bond, a carbon, or a divalent oxygen, sulfur, or —N(Z)— where Z is hydrogen, halogen, hydroxy, C₁₋₁₂ alkyl, C₁₋₁₂ alkoxy, C₆₋₁₂ aryl, or C₁₋₁₂ acyl; h is 0 to 2, j is 1 or 2, i is an integer of 0 or 1, and k is an integer of 0 to 3, with the proviso that at least two of R^(r), R^(p), R^(q) and R^(t) taken together are a fused cycloaliphatic, aromatic, or heteroaromatic ring. It will be understood that where the fused ring is aromatic, the ring as shown in formula (5) will have an unsaturated carbon-carbon linkage at the junction where the ring is fused. When i is 0, h is 0, and k is 1, the ring as shown in formula (5) contains 4 carbon atoms; when i is 0, h is 0, and k is 2, the ring as shown contains 5 carbon atoms, and when i is 0, h is 0, and k is 3, the ring contains 6 carbon atoms. In one example, two adjacent groups (e.g., R^(q) and R^(t) taken together) form an aromatic group, and in another embodiment, R^(q) and R^(t) taken together form one aromatic group and R^(r) and R^(p) taken together form a second aromatic group. When R^(q) and R^(t) taken together form an aromatic group, R^(p) can be a double-bonded oxygen atom, i.e., a ketone.

Other useful dihydroxy compounds having the formula HO—R¹—OH include aromatic dihydroxy compounds of formula (7):

wherein each R^(h) is independently a halogen atom, a C₁₋₁₀ hydrocarbyl such as a C₁₋₁₀ alkyl group, a halogen substituted C₁₋₁₀ hydrocarbyl such as a halogen-substituted C₁₋₁₀ alkyl group, and n is 0 to 4. The halogen is usually bromine.

Bisphenol-type dihydroxy aromatic compounds may include the following: 4,4′-dihydroxybiphenyl, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)diphenylmethane, bis(4-hydroxyphenyl)-1-naphthylmethane, 1,2-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane, bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 1,1-bis(hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxy-3 methyl phenyl)cyclohexane 1,1-bis(4-hydroxyphenyl)isobutene, 1,1-bis(4-hydroxyphenyl)cyclododecane, trans-2,3-bis(4-hydroxyphenyl)-2-butene, 2,2-bis(4-hydroxyphenyl)adamantine, (alpha,alpha′-bis(4-hydroxyphenyl)toluene, bis(4-hydroxyphenyl)acetonitrile, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(3-ethyl-4-hydroxyphenyl)propane, 2,2-bis(3-n-propyl-4-hydroxyphenyl)propane, 2,2-bis(3-isopropyl-4-hydroxyphenyl)propane, 2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane, 2,2-bis(3-t-butyl-4-hydroxyphenyl)propane, 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 2,2-bis(3-allyl-4-hydroxyphenyl)propane, 2,2-bis(3-methoxy-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene, 1,1-dibromo-2,2-bis(4-hydroxyphenyl)ethylene, 1,1-dichloro-2,2-bis(5-phenoxy-4-hydroxyphenyl)ethylene, 4,4′-dihydroxybenzophenone, 3,3-bis(4-hydroxyphenyl)-2-butanone, 1,6-bis(4-hydroxyphenyl)-1,6-hexanedione, ethylene glycol bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfone, 9,9-bis(4-hydroxyphenyl)fluorene, 2,7-dihydroxypyrene, 6,6′-dihydroxy-3,3,3′,3′-tetramethylspiro(bis)indane (“spirobiindane bisphenol”), 3,3-bis(4-hydroxyphenyl)phthalide, 2,6-dihydroxydibenzo-p-dioxin, 2,6-dihydroxythianthrene, 2,7-dihydroxyphenoxathin, 2,7-dihydroxy-9,10-dimethylphenazine, 3,6-dihydroxydibenzofuran, 3,6-dihydroxydibenzothiophene, and 2,7-dihydroxycarbazole, and the like, as well as a combination comprising at least one of the foregoing dihydroxy aromatic compounds.

Examples of the types of bisphenol compounds represented by formula (3) may include 1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (hereinafter “bisphenol A” or “BPA”), 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)n-butane, 2,2-bis(4-hydroxy-1-methylphenyl)propane, 1,1-bis(4-hydroxy-t-butylphenyl)propane, 3,3-bis(4-hydroxyphenyl)phthalimidine, 2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (“PBPP”), 9,9-bis(4-hydroxyphenyl)fluorene, and 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (“DMBPC”). Combinations comprising at least one of the foregoing dihydroxy aromatic compounds can also be used.

The dihydroxy compounds of formula (3) may exist in the form of the following formula (8):

wherein R₃ and R₅ are each independently a halogen or a C₁₋₁₆ alkyl group, R₄ is a C₁₋₁₆ alkyl, phenyl, or phenyl substituted with up to five halogens or C₁₋₆ alkyl groups, and c is 0 to 4. In a specific embodiment, R₄ is a C₁₋₁₆ alkyl or phenyl group. In still another embodiment, R₄ is a methyl or phenyl group. In another specific embodiment, each c is 0.

The dihydroxy compounds of formula (3) may be the following formula (9):

(also known as 3,3-bis(4-hydroxyphenyl)-2-phenylisoindolin-1-one (PPPBP)).

Alternatively, the dihydroxy compounds of formula (3) may have the following formula (10):

(also known as 4,4′-(1-phenylethane-1,1-diyl)diphenol(bisphenol AP) or 1,1-bis(4-hydroxyphenyl)-1-phenyl-ethane).

Alternatively, the dihydroxy compounds of formula (3) may have the following formula (11):

which is also known as 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, or 4,4′-(3,3,5-trimethylcyclohexane-1,1-diyl)diphenol(bisphenol TMC). When a copolycarbonate comprising polycarbonates derived from the formulas (9), (10) and (11) is used in the flame retardant compositions, it is generally used in amounts of 2 to 30 wt %, specifically 3 to 25 wt %, and more specifically 4 to 20 wt %, based on the total weight of the flame retardant composition.

Exemplary copolymers containing polycarbonate units may be derived from bisphenol A. In an embodiment, the polycarbonate composition may comprise a polyester-polycarbonate copolymer. A specific type of copolymer may be a polyestercarbonate, also known as a polyester-polycarbonate. As used herein, these terms (i.e., the polyestercarbonate and the polyester-polycarbonate) are synonymous. Such copolymers further contain, in addition to recurring carbonate chain units of the formula (1) as described above, repeating ester units of formula (12):

wherein O-D-O is a divalent group derived from a dihydroxy compound, and D may be, for example, one or more alkyl containing C₆-C₂₀ aromatic group(s), or one or more C₆-C₂₀ aromatic group(s), a C₂₋₁₀ alkylene group, a C₆₋₂₀ alicyclic group, a C₆₋₂₀ aromatic group or a polyoxyalkylene group in which the alkylene groups contain 2 to 6 carbon atoms, specifically 2, 3, or 4 carbon atoms. D may be a C₂₋₃₀ alkylene group having a straight chain, branched chain, or cyclic (including polycyclic) structure. O-D-O may be derived from an aromatic dihydroxy compound of formula (3) above. O-D-O may be derived from an aromatic dihydroxy compound of formula (4) above. O-D-O may be derived from an aromatic dihydroxy compound of formula (7) above.

The molar ratio of ester units to carbonate units in the copolymers may vary broadly, for example 1:99 to 99:1, specifically 10:90 to 90:10, and more specifically 25:75 to 75:25, depending on the desired properties of the final composition.

T of formula (12) may be a divalent group derived from a dicarboxylic acid, and may be, for example, a C₂₋₁₀ alkylene group, a C₆₋₂₀ alicyclic group, a C₆₋₂₀ alkyl aromatic group, a C₆₋₂₀ aromatic group, or a C₆ to C₃₆ divalent organic group derived from a dihydroxy compound or chemical equivalent thereof. In an embodiment, T is an aliphatic group. T may be derived from a C₆-C₂₀ linear aliphatic alpha-omega (αΩ) dicarboxylic ester.

Diacids from which the T group in the ester unit of formula (12) is derived include aliphatic dicarboxylic acid from 6 to 36 carbon atoms, optionally from 6 to 20 carbon atoms. The C₆-C₂₀ linear aliphatic alpha-omega (αΩ) dicarboxylic esters may be derived from adipic acid, sebacic acid, 3,3-dimethyl adipic acid, 3,3,6-trimethyl sebacic acid, 3,3,5,5-tetramethyl sebacic acid, azelaic acid, dodecanedioic acid, dimer acids, cyclohexane dicarboxylic acids, dimethyl cyclohexane dicarboxylic acid, norbornane dicarboxylic acids, adamantane dicarboxylic acids, cyclohexene dicarboxylic acids, C₁₄, C₁₈ and C₂₀ diacids.

In an embodiment, aliphatic alpha-omega dicarboxylic acids that may be reacted with a bisphenol to form a polyester include adipic acid, sebacic acid or dodecanedioic acid. Sebacic acid is a dicarboxylic acid having the following formula (13):

Sebacic acid has a molecular mass of 202.25 g/mol, a density of 1.209 g/cm³ (25° C.), and a melting point of 294.4° C. at 100 mm Hg. Sebacic acid may be derived from castor oil.

Other examples of aromatic dicarboxylic acids that may be used to prepare the polyester units include isophthalic or terephthalic acid, 1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether, 4,4′-bisbenzoic acid, and combinations comprising at least one of the foregoing acids. Acids containing fused rings can also be present, such as in 1,4-, 1,5-, or 2,6-naphthalenedicarboxylic acids. Specific dicarboxylic acids may be terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, sebacic acid, or combinations thereof.

Mixtures of the diacids can also be employed. It should be noted that although referred to as diacids, any ester precursor could be employed such as acid halides, specifically acid chlorides, and diaromatic esters of the diacid such as diphenyl, for example, the diphenylester of sebacic acid. The diacid carbon atom number does not include any carbon atoms that may be included in the ester precursor portion, for example diphenyl. It may be desirable that at least four, five, or six carbon bonds separate the acid groups. This may reduce the formation of undesirable and unwanted cyclic species. The aromatic dicarboxylic acids may be used in combination with the saturated aliphatic alpha-omega dicarboxylic acids to yield the polyester. In an exemplary embodiment, isophthalic acid or terephthalic acid may be used in combination with the sebacic acid to produce the polyester.

Overall, D of the polyester-polycarbonate may be a C₂₋₉ alkylene group and T is p-phenylene, m-phenylene, naphthalene, a divalent cycloaliphatic group, or a combination thereof. This class of polyester includes the poly(alkylene terephthalates).

The polyester-polycarbonate may have a bio-content (i.e., a sebacic acid content) according to ASTM-D-6866 of 2 weight percent (wt %) to 65 wt %, based on the total weight of the polycarbonate composition. In an embodiment, the polyester-polycarbonate may have a bio-content according to ASTM-D-6866 of at least 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 25 wt %, 30 wt %, 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt %, 60 wt % or 65 wt % of the composition derived therefrom. The polyester-polycarbonate may have a bio-content according to ASTM-D-6866 of at least 5 wt % of the polycarbonate composition. In other words, the polycarbonate composition may have at least 5 wt % of sebacic acid.

In an embodiment, two polycarbonate copolymers may be used in the flame retardant composition. The first polycarbonate copolymer comprises a polyester derived from sebacic acid that is copolymerized with a polycarbonate. The first polycarbonate polymer is endcapped with phenol or t-butyl-phenol. The second polycarbonate copolymer also comprises polyester units derived from sebacic acid that is copolymerized with a polycarbonate. The second polycarbonate copolymer is endcapped with para-cumyl phenol (PCP). The first polycarbonate has a lower molecular weight than the second polycarbonate copolymer.

The first polycarbonate copolymer has a weight average molecular weight of 15,000 to 28,000 Daltons, specifically 17,000 to 25,500 Daltons, specifically 19,000 to 23,000 Daltons, and more specifically 20,000 to 22,000 Daltons as measured by gel permeation chromatography using a polycarbonate standard. The first polycarbonate copolymer may comprise 3.0 mole % to 8.0 mole %, specifically 4.0 mole % to 7.5 mole %, and more specifically 5.0 mole % to 6.5 mole % of the polyester derived from sebacic acid.

The first polycarbonate copolymer is used in amounts of 10 to 60 wt %, specifically 15 to 58 wt %, specifically 20 to 55 wt %, and more specifically 23 to 52 wt %, based on the total weight of the flame retardant composition. In an exemplary embodiment, the first polycarbonate copolymer was present in an amount of 35 to 55 wt %, based on the total weight of the flame retardant composition.

In an embodiment, the second polycarbonate copolymer is endcapped with para-cumyl phenol and has a weight average molecular weight of 30,000 to 45,000 Daltons, specifically 32,000 to 40,000 Daltons, specifically 34,000 to 39,000 Daltons, more specifically 35,000 to 38,000 Daltons as measured by gel permeation chromatography using a polycarbonate standard. The second polycarbonate copolymer may comprise 7 mole % to 12 mole %, specifically 7.5 mole % to 10 mole %, and more specifically 8.0 mole % to 9.0 mole % of polyester derived from sebacic acid.

The second polycarbonate copolymer is used in amounts of 10 to 35 wt %, specifically 12 to 60 wt %, specifically 13 to 58 wt %, specifically 14 to 57 wt %, and more specifically 15 to 55 wt %, based on the total weight of the flame retardant composition.

Overall, the first and the second polycarbonate copolymers may contain 1 to 15 wt %, specifically 2 to 12 wt %, specifically 3 to 10 wt %, specifically 4 to 9 wt %, and more specifically 5 to 8 wt % of the polyester derived from sebacic acid. The polyester-polycarbonate copolymer may comprise 1.0 wt %, 2.0 wt %, 3.0 wt %, 4.0 wt %, 5.0 wt %, 6.0 wt %, 7.0 wt %, 8.0 wt %, 9.0 wt %, 10.0 wt %, 11.0 wt %, 12.0 wt %, 13.0 wt %, 14.0 wt %, and 15.0 wt % of a polyester derived from sebacic acid.

In one form, the first and second polycarbonate copolymers are polyester-polycarbonate copolymers where the polyester is derived by reacting by reacting sebacic acid with bisphenol A and where the polycarbonate is obtained from the reaction of bisphenol A with phosgene. The first and second polycarbonate copolymers containing the polyester-polycarbonate copolymer has the following formula (14):

Formula (14) may be designed to be a high flow ductile (HFD) polyester-polycarbonate copolymer (HFD). The high flow ductile copolymer has low molecular (LM) weight polyester units derived from sebacic acid. The polyester derived from sebacic acid in the high flow ductile copolymer is present in an amount of 6.0 mole % to 8.5 mole %. In an embodiment, the polyester derived from sebacic acid has a weight average molecular weight of 21,000 to 36,500 Daltons. In an exemplary embodiment, the high flow ductile polyester-polycarbonate copolymer may have a weight average molecular weight average of 21,500 Daltons as measured by gel permeation chromatography using a polycarbonate standard. It is desirable for the high flow ductile polyester-polycarbonate copolymer to contain 6.0 mole % derived from sebacic acid.

The first and the second polycarbonate copolymer which comprises the polyester-polycarbonate copolymers beneficially have a low level of carboxylic anhydride groups. Anhydride groups are where two aliphatic diacids, or chemical equivalents, react to form an anhydride linkage. The amount of carboxylic acid groups bound in such anhydride linkages should be less than or equal to 10 mole % of the total amount of carboxylic acid content in the copolymer. In other embodiments, the anhydride content should be less than or equal to 5 mole % of carboxylic acid content in the copolymer, and in yet other embodiments, the carboxylic acid content in the copolymer should be less than or equal to 2 mole %.

Low levels of anhydride groups can be achieved by conducting an interfacial polymerization reaction of the dicarboxylic acid, bisphenol and phosgene initially at a low pH (4 to 6) to get a high incorporation of the diacid in the polymer, and then after a proportion of the monomer has been incorporated into the growing polymer chain, switching to a high pH (10 to 11) to convert any anhydride groups into ester linkages. Anhydride linkages can be determined by numerous methods such as, for instance proton NMR analyses showing signal for the hydrogens adjacent to the carbonyl group. In an embodiment, the first and the second polycarbonate copolymer have a low amount of anhydride linkages, such as, for example, less than or equal to 5 mole %, specifically less than or equal to 3 mole %, and more specifically less than or equal to 2 mole %, as determined by proton NMR analysis. Low amounts of anhydride linkages in the polyester-polycarbonate copolymer contribute to superior melt stability in the copolymer, as well as other desirable properties.

Useful polyesters that can be copolymerized with polycarbonate can include aromatic polyesters, poly(alkylene esters) including poly(alkylene arylates), and poly(cycloalkylene diesters). Aromatic polyesters can have a polyester structure according to formula (12), wherein D and T are each aromatic groups as described hereinabove. In an embodiment, useful aromatic polyesters can include, for example, poly(isophthalate-terephthalate-resorcinol) esters, poly(isophthalate-terephthalate-bisphenol A) esters, poly[(isophthalate-terephthalate-resorcinol) ester-co-(isophthalate-terephthalate-bisphenol A)]ester, or a combination comprising at least one of these. Also contemplated are aromatic polyesters with a minor amount, e.g., 0.5 to 10 weight percent, based on the total weight of the polyester, of units derived from an aliphatic diacid and/or an aliphatic polyol to make copolyesters. Poly(alkylene arylates) can have a polyester structure according to formula (12), wherein T comprises groups derived from aromatic dicarboxylates, cycloaliphatic dicarboxylic acids, or derivatives thereof. Examples of specifically useful T groups include 1,2-, 1,3-, and 1,4-phenylene; 1,4- and 1,5-naphthylenes; cis- or trans-1,4-cyclohexylene; and the like. Specifically, where T is 1,4-phenylene, the poly(alkylene arylate) is a poly(alkylene terephthalate). In addition, for poly(alkylene arylate), specifically useful alkylene groups D include, for example, ethylene, 1,4-butylene, and bis-(alkylene-disubstituted cyclohexane) including cis- and/or trans-1,4-(cyclohexylene)dimethylene. Examples of poly(alkylene terephthalates) include poly(ethylene terephthalate) (PET), poly(1,4-butylene terephthalate) (PBT), and polypropylene terephthalate) (PPT). Also useful are poly(alkylene naphthoates), such as poly(ethylene naphthanoate) (PEN), and poly(butylene naphthanoate) (PBN). A specifically useful poly(cycloalkylene diester) is poly(cyclohexanedimethylene terephthalate) (PCT). Combinations comprising at least one of the foregoing polyesters can also be used.

Copolymers comprising alkylene terephthalate repeating ester units with other ester groups can also be useful. Specifically useful ester units can include different alkylene terephthalate units, which can be present in the polymer chain as individual units, or as blocks of poly(alkylene terephthalates). Copolymers of this type include poly(cyclohexanedimethylene terephthalate)-co-poly(ethylene terephthalate), abbreviated as PETG where the polymer comprises greater than or equal to 50 mol % of poly(ethylene terephthalate), and abbreviated as PCTG where the polymer comprises greater than 50 mol % of poly(1,4-cyclohexanedimethylene terephthalate).

Poly(cycloalkylene diester)s can also include poly(alkylene cyclohexanedicarboxylate)s. Of these, a specific example is poly(1,4-cyclohexane-dimethanol-1,4-cyclohexanedicarboxylate) (PCCD), having recurring units of formula (14a)

wherein, as described using formula (12), D is a 1,4-cyclohexanedimethylene group derived from 1,4-cyclohexanedimethanol, and T is a cyclohexane ring derived from cyclohexanedicarboxylate or a chemical equivalent thereof, and can comprise the cis-isomer, the trans-isomer, or a combination comprising at least one of the foregoing isomers.

The polycarbonate and polyester can be used in a weight ratio of 1:99 to 99:1, specifically 10:90 to 90:10, and more specifically 30:70 to 70:30, depending on the function and properties desired.

It is desirable for such a polyester and polycarbonate blend to have an MVR of 5 to 150 cc/10 min., specifically 7 to 125 cc/10 min, more specifically 9 to 110 cc/10 min, and still more specifically 10 to 100 cc/10 min., measured at 300° C. and a load of 1.2 kilograms according to ASTM D1238-04.

In an exemplary embodiment, the polycarbonate composition comprises a copolyestercarbonate comprising poly(1,4-cyclohexane-dimethanol-1,4-cyclohexanedicarboxylate) (PCCD). The copolyestercarbonate is present in an amount of 5 to 25 wt %, specifically 6 to 15 wt %, and more specifically 7 to 12 wt %, based on the total weight of the flame retardant composition.

Polycarbonates may be manufactured by processes such as interfacial polymerization and melt polymerization. Copolycarbonates having a high glass transition temperature are generally manufactured using interfacial polymerization. Although the reaction conditions for interfacial polymerization can vary, an exemplary process generally involves dissolving or dispersing a dihydric phenol reactant in aqueous caustic soda or potash, adding the resulting mixture to a water-immiscible solvent medium, and contacting the reactants with a carbonate precursor in the presence of a catalyst such as, for example, a tertiary amine or a phase transfer catalyst, under controlled pH conditions, e.g., 8 to 10. The most commonly used water immiscible solvents include methylene chloride, 1,2-dichloroethane, chlorobenzene, toluene, and the like.

Exemplary carbonate precursors may include, for example, a carbonyl halide such as carbonyl bromide or carbonyl chloride, or a haloformate such as a bishaloformates of a dihydric phenol (e.g., the bischloroformates of bisphenol A, hydroquinone, or the like) or a glycol (e.g., the bishaloformate of ethylene glycol, neopentyl glycol, polyethylene glycol, or the like). Combinations comprising at least one of the foregoing types of carbonate precursors can also be used. For example, an interfacial polymerization reaction to form carbonate linkages uses phosgene as a carbonate precursor, and is referred to as a phosgenation reaction.

Among tertiary amines that can be used are aliphatic tertiary amines such as triethylamine, tributylamine, cycloaliphatic amines such as N,N-diethyl-cyclohexylamine, and aromatic tertiary amines such as N,N-dimethylaniline.

Among the phase transfer catalysts that can be used are catalysts of the formula (R³)₄Q⁺X, wherein each R³ is the same or different, and is a C₁₋₁₀ alkyl group; Q is a nitrogen or phosphorus atom; and X is a halogen atom or a C₁₋₈ alkoxy group or C₆₋₁₈ aryloxy group. Exemplary phase transfer catalysts include, for example, [CH₃(CH₂)₃]₄NX, [CH₃(CH₂)₃]₄PX, [CH₃(CH₂)₅]₄NX, [CH₃(CH₂)₆]₄NX, [CH₃(CH₂)₄]₄NX, CH₃—[CH₃(CH₂)₃]₃NX, and CH₃—[CH₃(CH₂)₂]₃NX, wherein X is CL, Br⁻, a C₁₋₈ alkoxy group or a C₆₋₁₈ aryloxy group. An effective amount of a phase transfer catalyst can be 0.1 to 10 wt % based on the weight of bisphenol in the phosgenation mixture. For example, an effective amount of phase transfer catalyst can be 0.5 to 2 wt % based on the weight of bisphenol in the phosgenation mixture.

Alternatively, melt processes can be used to make the polycarbonates. Melt polymerization may be conducted as a batch process or as a continuous process. In either case, the melt polymerization conditions used may comprise two or more distinct reaction stages, for example, a first reaction stage in which the starting dihydroxy aromatic compound and diaryl carbonate are converted into an oligomeric polycarbonate and a second reaction stage wherein the oligomeric polycarbonate formed in the first reaction stage is converted to high molecular weight polycarbonate. Such “staged” polymerization reaction conditions are especially suitable for use in continuous polymerization systems wherein the starting monomers are oligomerized in a first reaction vessel and the oligomeric polycarbonate formed therein is continuously transferred to one or more downstream reactors in which the oligomeric polycarbonate is converted to high molecular weight polycarbonate. Typically, in the oligomerization stage the oligomeric polycarbonate produced has a number average molecular weight of 1,000 to 7,500 Daltons. In one or more subsequent polymerization stages the number average molecular weight (Mn) of the polycarbonate is increased to between 8,000 and 25,000 Daltons (using polycarbonate standard).

The term “melt polymerization conditions” is understood to mean those conditions necessary to effect reaction between a dihydroxy aromatic compound and a diaryl carbonate in the presence of a transesterification catalyst. Typically, solvents are not used in the process, and the reactants dihydroxy aromatic compound and the diaryl carbonate are in a molten state. The reaction temperature can be 100° C. to 350° C., specifically 180° C. to 310° C. The pressure may be at atmospheric pressure, supra-atmospheric pressure, or a range of pressures from atmospheric pressure to 15 ton in the initial stages of the reaction, and at a reduced pressure at later stages, for example 0.2 to 15 torr. The reaction time is generally 0.1 hours to 10 hours.

The diaryl carbonate ester can be diphenyl carbonate, or an activated diphenyl carbonate having electron-withdrawing substituents on the aryl groups, such as bis(4-nitrophenyl)carbonate, bis(2-chlorophenyl)carbonate, bis(4-chlorophenyl)carbonate, bis(methyl salicyl)carbonate, bis(4-methylcarboxylphenyl)carbonate, bis(2-acetylphenyl)carboxylate, bis(4-acetylphenyl)carboxylate, or a combination comprising at least one of the foregoing.

Catalysts used in the melt polymerization of polycarbonates can include alpha or beta catalysts. Beta catalysts are typically volatile and degrade at elevated temperatures. Beta catalysts are therefore preferred for use at early low-temperature polymerization stages. Alpha catalysts are typically more thermally stable and less volatile than beta catalysts.

The alpha catalyst can comprise a source of alkali or alkaline earth ions. The sources of these ions include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, as well as alkaline earth hydroxides such as magnesium hydroxide and calcium hydroxide. Other possible sources of alkali and alkaline earth metal ions include the corresponding salts of carboxylic acids (such as sodium acetate) and derivatives of ethylene diamine tetraacetic acid (EDTA) (such as EDTA tetrasodium salt, and EDTA magnesium disodium salt). Other alpha transesterification catalysts include alkali or alkaline earth metal salts of a non-volatile inorganic acid such as NaH₂PO₃, NaH₂PO₄, Na₂HPO₃, KH₂PO₄, CsH₂PO₄, Cs₂HPO₄, and the like, or mixed salts of phosphoric acid, such as NaKHPO₄, CsNaHPO₄, CsKHPO₄, and the like. Combinations comprising at least one of any of the foregoing catalysts can be used.

Possible beta catalysts can comprise a quaternary ammonium compound, a quaternary phosphonium compound, or a combination comprising at least one of the foregoing. The quaternary ammonium compound can be a compound of the structure (R⁴)₄N⁺X⁻, wherein each R⁴ is the same or different, and is a C₁₋₂₀ alkyl group, a C₄₋₂₀ cycloalkyl group, or a C₄₋₂₀ aryl group; and X⁻ is an organic or inorganic anion, for example a hydroxide, halide, carboxylate, sulfonate, sulfate, formate, carbonate, or bicarbonate. Examples of organic quaternary ammonium compounds include tetramethyl ammonium hydroxide, tetrabutyl ammonium hydroxide, tetramethyl ammonium acetate, tetramethyl ammonium formate, tetrabutyl ammonium acetate, and combinations comprising at least one of the foregoing. Tetramethyl ammonium hydroxide is often used. The quaternary phosphonium compound can be a compound of the structure (R⁵)₄P⁺X⁻, wherein each R⁵ is the same or different, and is a C₁₋₂₀ alkyl group, a C₄₋₂₀ cycloalkyl group, or a C₄₋₂₀ aryl group; and X⁻is an organic or inorganic anion, for example a hydroxide, halide, carboxylate, sulfonate, sulfate, formate, carbonate, or bicarbonate. Where X⁻ is a polyvalent anion such as carbonate or sulfate it is understood that the positive and negative charges in the quaternary ammonium and phosphonium structures are properly balanced. For example, where R²⁰-R²³ are each methyl groups and X⁻is carbonate, it is understood that X⁻ represents 2(CO₃ ⁻²). Examples of organic quaternary phosphonium compounds include tetramethyl phosphonium hydroxide, tetramethyl phosphonium acetate, tetramethyl phosphonium formate, tetrabutyl phosphonium hydroxide, tetrabutyl phosphonium acetate (TBPA), tetraphenyl phosphonium acetate, tetraphenyl phosphonium phenoxide, and combinations comprising at least one of the foregoing. TBPA is often used.

The amount of alpha and beta catalyst used can be based upon the total number of moles of dihydroxy compound used in the polymerization reaction. When referring to the ratio of beta catalyst, for example a phosphonium salt, to all dihydroxy compounds used in the polymerization reaction, it is convenient to refer to moles of phosphonium salt per mole of the dihydroxy compound, meaning the number of moles of phosphonium salt divided by the sum of the moles of each individual dihydroxy compound present in the reaction mixture. The alpha catalyst can be used in an amount sufficient to provide 1×10⁻² to 1×10⁻⁸ moles, specifically, 1×10⁻⁴ to 1×10⁻⁷ moles of metal per mole of the dihydroxy compounds used. The amount of beta catalyst (e.g., organic ammonium or phosphonium salts) can be 1×10⁻² to 1×10⁻⁵, specifically 1×10⁻³ to 1×10⁻⁴ moles per total mole of the dihydroxy compounds in the reaction mixture.

All types of polycarbonate end groups are contemplated as being useful in the high and low glass transition temperature polycarbonates, provided that such end groups do not significantly adversely affect desired properties of the compositions. An end-capping agent (also referred to as a chain-stopper) can be used to limit molecular weight growth rate, and so control molecular weight of the first and/or second polycarbonate. Exemplary chain-stoppers include certain monophenolic compounds (i.e., phenyl compounds having a single free hydroxy group), monocarboxylic acid chlorides, and/or monochloroformates. Phenolic chain-stoppers are exemplified by phenol and C₁-C₂₂ alkyl-substituted phenols such as para-cumyl-phenol, resorcinol monobenzoate, and p- and tertiary-butyl phenol, cresol, and monoethers of diphenols, such as p-methoxyphenol. Alkyl-substituted phenols with branched chain alkyl substituents having 8 to 9 carbon atoms can be specifically mentioned. In an embodiment, at least one of the copolymers is endcapped with para-cumyl phenol (PCP).

Endgroups can be derived from the carbonyl source (i.e., the diaryl carbonate), from selection of monomer ratios, incomplete polymerization, chain scission, and the like, as well as any added end-capping groups, and can include derivatizable functional groups such as hydroxy groups, carboxylic acid groups, or the like. In an embodiment, the endgroup of a polycarbonate can comprise a structural unit derived from a diaryl carbonate, where the structural unit can be an endgroup. In a further embodiment, the endgroup is derived from an activated carbonate. Such endgroups can derive from the transesterification reaction of the alkyl ester of an appropriately substituted activated carbonate, with a hydroxy group at the end of a polycarbonate polymer chain, under conditions in which the hydroxy group reacts with the ester carbonyl from the activated carbonate, instead of with the carbonate carbonyl of the activated carbonate. In this way, structural units derived from ester containing compounds or substructures derived from the activated carbonate and present in the melt polymerization reaction can form ester endgroups. In an embodiment, the ester endgroup derived from a salicylic ester can be a residue of BMSC or other substituted or unsubstituted bis(alkyl salicyl)carbonate such as bis(ethyl salicyl)carbonate, bis(propyl salicyl)carbonate, bis(phenyl salicyl)carbonate, bis(benzyl salicyl)carbonate, or the like. In a specific embodiment, where BMSC is used as the activated carbonyl source, the endgroup is derived from and is a residue of BMSC, and is an ester endgroup derived from a salicylic acid ester, having the structure of formula (15):

The reactants for the polymerization reaction using an activated aromatic carbonate can be charged into a reactor either in the solid form or in the molten form. Initial charging of reactants into a reactor and subsequent mixing of these materials under reactive conditions for polymerization may be conducted in an inert gas atmosphere such as a nitrogen atmosphere. The charging of one or more reactant may also be done at a later stage of the polymerization reaction. Mixing of the reaction mixture is accomplished by stirring or other forms of agitation. Reactive conditions include time, temperature, pressure and other factors that affect polymerization of the reactants. In an embodiment, the activated aromatic carbonate is added at a mole ratio of 0.8 to 1.3, and more specifically 0.9 to 1.3, and all sub-ranges there between, relative to the total moles of monomer unit compounds. In a specific embodiment, the molar ratio of activated aromatic carbonate to monomer unit compounds is 1.013 to 1.29, specifically 1.015 to 1.028. In another specific embodiment, the activated aromatic carbonate is BMSC.

Branched polycarbonate blocks can be prepared by adding a branching agent during polymerization. These branching agents include polyfunctional organic compounds containing at least three functional groups selected from hydroxyl, carboxyl, carboxylic anhydride, haloformyl, and mixtures of the foregoing functional groups. Specific examples include trimellitic acid, trimellitic anhydride, tris-phenol TC (1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene), tris-phenol PA (4(4(1,1-bis(p-hydroxyphenyl)-ethyl)alpha,alpha-dimethyl benzyl)phenol), 4-chloroformyl phthalic anhydride, trimesic acid, and benzophenone tetracarboxylic acid. Combinations comprising linear polycarbonates and branched polycarbonates can be used.

In some embodiments, a particular type of branching agent is used to create branched polycarbonate materials. These branched polycarbonate materials have statistically more than two end groups. The branching agent is added in an amount (relative to the bisphenol monomer) that is sufficient to achieve the desired branching content, that is, more than two end groups. The molecular weight of the polymer may become very high upon addition of the branching agent, and to avoid excess viscosity during polymerization, an increased amount of a chain stopper agent can be used, relative to the amount used when the particular branching agent is not present. The amount of chain stopper used is generally above 5 mole percent and less than 20 mole percent compared to the bisphenol monomer.

Such branching agents include aromatic triacyl halides, for example triacyl chlorides of formula (16)

wherein Z is a halogen, C₁₋₃ alkyl, C₁₋₃ alkoxy, C₇₋₁₂ arylalkylene, C₇₋₁₂ alkylarylene, or nitro, and z is 0 to 3; a tri-substituted phenol of formula (17)

wherein T is a C₁₋₂₀ alkyl, C₁₋₂₀ alkyleneoxy, C₇₋₁₂ arylalkyl, or C₇₋₁₂ alkylaryl, Y is a halogen, C₁₋₃ alkyl, C₁₋₃ alkoxy, C₇₋₁₂ arylalkyl, C₇₋₁₂ alkylaryl, or nitro, s is 0 to 4; or a compound of formula (18) (isatin-bis-phenol).

Examples of specific branching agents that are particularly effective in the compositions include trimellitic trichloride (TMTC), tris-p-hydroxyphenylethane (THPE), and isatin-bis-phenol.

The amount of the branching agents used in the manufacture of the polymer will depend on a number of considerations, for example the type of R¹ groups, the amount of chain stopper, e.g., cyanophenol, and the desired molecular weight of the polycarbonate. In general, the amount of branching agent is effective to provide 0.1 to 10 branching units per 100 R¹ units, specifically 0.5 to 8 branching units per 100 R¹ units, and more specifically 0.75 to 5 branching units per 100 R¹ units. For branching agents having formula (16), the branching agent triester groups are present in an amount of 0.1 to 10 branching units per 100 R¹ units, specifically 0.5 to 8 branching units per 100 R¹ units, and more specifically 0.75 to 5 branching agent triester units per 100 R¹ units. For branching agents having formula (17) or (18), the branching agent triphenyl carbonate groups formed are present in an amount of 0.1 to 10 branching units per 100 R¹ units, specifically 0.5 to 8 branching units per 100 R¹ units, and more specifically 0.75 to 5 triphenylcarbonate units per 100 R¹ units. In some embodiments, a combination of two or more branching agents may be used. Alternatively, the branching agents can be added at a level of 0.05 to 2.0 wt. %.

In an embodiment, the polycarbonate is a branched polycarbonate comprising units as described above; greater than or equal to 3 mole %, based on the total moles of the polycarbonate, of moieties derived from a branching agent; and end-capping groups derived from an end-capping agent having a pKa between 8.3 and 11. The branching agent can comprise trimellitic trichloride, 1,1,1-tris(4-hydroxyphenyl)ethane or a combination of trimellitic trichloride and 1,1,1-tris(4-hydroxyphenyl)ethane, and the end-capping agent is phenol or a phenol containing a substituent of cyano group, aliphatic groups, olefinic groups, aromatic groups, halogens, ester groups, ether groups, or a combination comprising at least one of the foregoing. In a specific embodiment, the end-capping agent is phenol, p-t-butylphenol, p-methoxyphenol, p-cyanophenol, p-cumylphenol, or a combination comprising at least one of the foregoing.

As noted above, the polycarbonate composition may include a linear polycarbonate, a branched polycarbonate, or a mixture of a linear and a branched polycarbonate. When the polycarbonate composition includes a mixture of a linear and a branched polycarbonate, the branched polycarbonate is used in amounts of 5 to 95 wt %, specifically 10 to 25 wt % and more specifically 12 to 20 wt %, based on the total weight of the polycarbonate composition. Linear polycarbonates are used in amounts of 5 to 95 wt %, specifically 20 to 60 wt %, and more specifically 25 to 55 wt %, based on the total weight of the polycarbonate composition.

In an embodiment, the polycarbonate composition comprises post-consumer recycle (PCR) polycarbonate derived from previously manufactured articles (e.g., soda bottles, water bottles, and the like) that comprise polycarbonate. The PCR materials occasionally comprise a polyester, which degrades the flame retardancy characteristics. The polyester present in the PCR polycarbonate is generally present in an amount of 0.05 to 1 wt %, specifically 0.1 to 0.25 wt %, based on the total weight of the PCR polycarbonate. When PCR polycarbonate is used in the flame retardant composition, it is present in amounts of 20 to 60 wt %, specifically 40 to 55 wt %., based on the total weight of the flame retardant composition.

A linear polycarbonate may be used in the polycarbonate composition in amounts of 30 to 90 wt %, specifically 35 to 85 wt %, and more specifically 37 to 80 wt %, based on the total weight of the flame retardant composition, while the branched polycarbonate may be used in amounts of 10 to 70 wt %, specifically 15 to 60 wt %, and more specifically in amounts of 17 to 55 wt %, based on the total weight of the flame retardant composition. The polycarbonate composition is used in amounts of 20 to 90 wt %, specifically 30 to 85 wt %, and more specifically 40 to 80 wt %, based on the total weight of the flame retardant composition.

The polycarbonate composition may further comprise a polysiloxane-polycarbonate copolymer, also referred to as a polysiloxane-carbonate copolymer. The polydiorganosiloxane (also referred to herein as “polysiloxane”) blocks of the copolymer comprise repeating diorganosiloxane units as in formula (19)

wherein each R is independently a C₁₋₁₃ monovalent organic group. For example, R can be a C₁-C₁₃ alkyl, C₁-C₁₃ alkoxy, C₂-C₁₃ alkenyl group, C₂-C₁₃ alkenyloxy, C₃-C₆ cycloalkyl, C₃-C₆ cycloalkoxy, C₆-C₁₄ aryl, C₆-C₁₀ aryloxy, C₇-C₁₃ arylalkyl, C₇-C₁₃ aralkoxy, C₇-C₁₃ alkylaryl, or C₇-C₁₃ alkylaryloxy. The foregoing groups can be fully or partially halogenated with fluorine, chlorine, bromine, or iodine, or a combination thereof. Combinations of the foregoing R groups can be used in the same copolymer.

The value of E in formula (19) can vary widely depending on the type and relative amount of each component in the flame retardant composition, the desired properties of the composition, and like considerations. Generally, E has an average value of 2 to 1,000, specifically 3 to 500, more specifically 5 to 100. In an embodiment, E has an average value of 10 to 75, and in still another embodiment, E has an average value of 40 to 60. Where E is of a lower value, e.g., less than 40, it can be desirable to use a relatively larger amount of the polycarbonate-polysiloxane copolymer. Conversely, where E is of a higher value, e.g., greater than 40, a relatively lower amount of the polycarbonate-polysiloxane copolymer can be used.

A combination of a first and a second (or more) polycarbonate-polysiloxane copolymers can be used, wherein the average value of E of the first copolymer is less than the average value of E of the second copolymer.

In an embodiment, the polysiloxane blocks are of formula (20)

wherein E is as defined above; each R can be the same or different, and is as defined above; and Ar can be the same or different, and is a substituted or unsubstituted C₆-C₃₀ arylene group, wherein the bonds are directly connected to an aromatic moiety. Ar groups in formula (20) can be derived from a C₆-C₃₀ dihydroxyarylene compound, for example a dihydroxyarylene compound of formula (4) or (6) above. Exemplary dihydroxyarylene compounds are 1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)n-butane, 2,2-bis(4-hydroxy-1-methylphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl sulfide), and 1,1-bis(4-hydroxy-t-butylphenyl)propane. Combinations comprising at least one of the foregoing dihydroxy compounds can also be used.

In another embodiment, polysiloxane blocks are of formula (21)

wherein R and E are as described above, and each R⁵ is independently a divalent C₁-C₃₀ organic group, and wherein the polymerized polysiloxane unit is the reaction residue of its corresponding dihydroxy compound. In a specific embodiment, the polysiloxane blocks are of formula (22):

wherein R and E are as defined above. R⁶ in formula (22) is a divalent C₂-C₈ aliphatic group. Each M in formula (22) can be the same or different, and can be a halogen, cyano, nitro, C₁-C₈ alkylthio, C₁-C₈ alkyl, C₁-C₈ alkoxy, C₂-C₈ alkenyl, C₂-C₈ alkenyloxy group, C₃-C₈ cycloalkyl, C₃-C₈ cycloalkoxy, C₆-C₁₀ aryl, C₆-C₁₀ aryloxy, C₇-C₁₂ aralkyl, C₇-C₁₂ aralkoxy, C₇-C₁₂ alkylaryl, or C₇-C₁₂ alkylaryloxy, wherein each n is independently 0, 1, 2, 3, or 4.

In an embodiment, M is bromo or chloro, an alkyl group such as methyl, ethyl, or propyl, an alkoxy group such as methoxy, ethoxy, or propoxy, or an aryl group such as phenyl, chlorophenyl, or tolyl; R⁶ is a dimethylene, trimethylene or tetramethylene group; and R is a C₁₋₈ alkyl, haloalkyl such as trifluoropropyl, cyanoalkyl, or aryl such as phenyl, chlorophenyl or tolyl.

In another embodiment, R is methyl, or a combination of methyl and trifluoropropyl, or a combination of methyl and phenyl. In still another embodiment, M is methoxy, n is one, R⁶ is a divalent C₁-C₃ aliphatic group, and R is methyl.

Specific polydiorganosiloxane blocks are of the formula

or a combination comprising at least one of the foregoing, wherein E has an average value of 2 to 200, 2 to 125, 5 to 125, 5 to 100, 5 to 50, 20 to 80, or 5 to 20.

In an embodiment, locks of formula (19) can be derived from the corresponding dihydroxy polysiloxane (23)

wherein R, E, M, R⁶, and n are as described above. Such dihydroxy polysiloxanes can be made by effecting a platinum-catalyzed addition between a siloxane hydride of formula (24)

wherein R and E are as previously defined, and an aliphatically unsaturated monohydric phenol. Exemplary aliphatically unsaturated monohydric phenols include eugenol, 2-alkylphenol, 4-allyl-2-methylphenol, 4-allyl-2-phenylphenol, 4-allyl-2-bromophenol, 4-allyl-2-t-butoxyphenol, 4-phenyl-2-phenylphenol, 2-methyl-4-propylphenol, 2-allyl-4,6-dimethylphenol, 2-allyl-4-bromo-6-methylphenol, 2-allyl-6-methoxy-4-methylphenol and 2-allyl-4,6-dimethylphenol. Combinations comprising at least one of the foregoing can also be used.

The polysiloxane-polycarbonate copolymer can comprise 50 to 99 weight percent of carbonate units and 1 to 50 weight percent siloxane units. Within this range, the polyorganosiloxane-polycarbonate copolymer can comprise 70 to 98 weight percent, more specifically 75 to 97 weight percent of carbonate units and 2 to 30 weight percent, more specifically 3 to 25 weight percent siloxane units. In an exemplary embodiment, the polysiloxane-polycarbonate copolymer is endcapped with para-cumyl phenol.

In an embodiment, an exemplary polysiloxane-polycarbonate copolymer is a block copolymer having the structure shown in the Formula (25) below:

where the polysiloxane blocks are endcapped with eugenol, where x is about 1 to about 100, specifically about 5 to about 85, specifically about 10 to about 70, specifically about 15 to about 65, and more specifically about 40 to about 60. In one embodiment, y is about 1 to about 90 and z is about 1 to about 600. The polysiloxane block may be randomly distributed or controlled distributed amongst the polycarbonate blocks. In one embodiment, x is about 30 to about 50, y is about 10 to about 30 and z is about 450 to about 600.

In one embodiment, the polysiloxane-polycarbonate copolymer comprises about 10 wt % or less, specifically about 6 wt % or less, and more specifically about 4 wt % or less, of the polysiloxane based on the total weight of the polysiloxane-polycarbonate copolymer. Polysiloxane-polycarbonate copolymers containing 10 wt % or less are generally optically transparent and are sometimes referred to as EXL-T as commercially available from Sabic Innovative Plastics.

In another embodiment, the polysiloxane-polycarbonate copolymer comprises about 10 wt % or more, specifically about 12 wt % or more, and more specifically about 14 wt % or more, of the polysiloxane copolymer based on the total weight of the polysiloxane-polycarbonate copolymer. Polysiloxane-polycarbonate copolymers containing 10 wt % or more are generally optically opaque and are sometimes referred to as EXL-P as commercially available from Sabic Innovative Plastics.

When the polysiloxane polycarbonate copolymer comprises eugenol endcapped polysiloxane, the flame retardant composition comprises 5 to 85 wt % of the polysiloxane-polycarbonate copolymer. The polysiloxane content is 1 to 25 wt %, specifically 1 to 16 wt %, specifically 2 to 14 wt %, and more specifically 3 to 6 wt %, based on the total weight of the polysiloxane-polycarbonate copolymer. In an embodiment, the weight average molecular weight of the polysiloxane block is 25,000 to 30,000 Daltons using gel permeation chromatography with a bisphenol A polycarbonate absolute molecular weight standard. In an exemplary embodiment, the polysiloxane content is 15 to 25 wt %, based on the total weight of the polysiloxane-polycarbonate copolymer.

The polysiloxane polycarbonate copolymer can have a weight average molecular weight of 2,000 to 100,000 Daltons, specifically 5,000 to 50,000 Daltons as measured by gel permeation chromatography using a crosslinked styrene-divinyl benzene column, at a sample concentration of 1 milligram per milliliter, and as calibrated with polycarbonate standards. In an embodiment, the polysiloxane polycarbonate copolymer can have a weight average molecular weight of greater than or equal to 30,000 Daltons, specifically greater than or equal to 31,000 Daltons, and more specifically greater than or equal to 32,000 Daltons as measured by gel permeation chromatography using a crosslinked styrene-divinyl benzene column, at a sample concentration of 1 milligram per milliliter, and as calibrated with polycarbonate standards.

The polysiloxane polycarbonate copolymer can have a melt volume flow rate, measured at 300° C./1.2 kg, of 1 to 50 cubic centimeters per 10 minutes (cc/10 min), specifically 2 to 30 cc/10 min. Mixtures of polysiloxane polycarbonate copolymer of different flow properties can be used to achieve the overall desired flow property.

The polysiloxane-polycarbonate copolymer is used in amounts of 5 to 50 wt %, specifically amounts of 7 to 22 wt %, and more specifically in amounts of 8 to 20 wt %, based on the total weight of the flame retardant composition.

The flame retardant composition may also optionally contain additives such as antioxidants, antiozonants, stabilizers, thermal stabilizers, mold release agents, dyes, colorants, pigments, flow modifiers, or the like, or a combination comprising at least one of the foregoing additives.

As noted above, the flame retardant composition comprises a flame retarding agent. The flame retarding agent is a phosphazene compound. In an embodiment, the flame retarding agent is a phosphazene oligomer.

The phosphazene compound used in the flame retardant composition is an organic compound having a —P═N— bond in the molecule. In an embodiment, the phosphazene compound comprises at least one species of the compound selected from the group consisting of a cyclic phenoxyphosphazene represented by the formula (16) below; a chainlike phenoxyphosphazene represented by the formula (17) below; and a crosslinked phenoxyphosphazene compound obtained by crosslinking at least one species of phenoxyphosphazene selected from those represented by the formulae (16) and (17) below, with a crosslinking group represented by the formula (18) below:

where in the formula (16), m represents an integer of 3 to 25, and Ph represents a phenyl group, R₁ and R₂ are the same or different and are independently a hydrogen, a hydroxyl, a C₁₋₁₂ alkoxy, or a C₁₋₁₂ alkyl.

The chainlike phenoxyphosphazene represented by the formula (17) below:

where in the formula (17), X¹ represents a —N═P(OPh)₃ group or a —N═P(O)OPh group, Y¹ represents a —P(OPh)₄ group or a —P(O) (OPh)₂ group, n represents an integer from 3 to 10000, Ph represents a phenyl group, R1 and R2 are the same or different and are independently a hydrogen, a halogen, a C₁₋₁₂ alkoxy, or a C₁₋₁₂ alkyl.

The phenoxyphosphazenes may also have a crosslinking group represented by the formula (18) below:

where in the formula (18), A represents —C(CH3)₂-, —SO₂—, —S—, or —O—, and q is 0 or 1.

In an embodiment, the phenoxyphosphazene compound has a structure represented by the formula (19)

where R1 to R6 can be the same of different and can be an aryl group, an aralkyl group, a C₁₋₁₂ alkoxy, a C₁₋₁₂ alkyl, or a combination thereof.

In an embodiment, the phenoxyphosphazene compound has a structure represented by the formula (20)

Commercially available phenoxyphosphazenes having the foregoing structures are LY202® manufactured and distributed by Lanyin Chemical Co., Ltd, FP-110® manufactured and distributed by Fushimi Pharmaceutical Co., Ltd., and SPB-100® manufactured and distributed by Otsuka Chemical Co., Ltd.

The cyclic phenoxyphosphazene compound represented by the formula (16) may be exemplified by compounds such as phenoxy cyclotriphosphazene, octaphenoxy cyclotetraphosphazene, and decaphenoxy cyclopentaphosphazene, obtained by allowing ammonium chloride and phosphorus pentachloride to react at 120 to 130° C. to obtain a mixture containing cyclic and straight chain chlorophosphazenes, extracting cyclic chlorophosphazenes such as hexachloro cyclotriphosphazene, octachloro cyclotetraphosphazene, and decachloro cyclopentaphosphazene, and then substituting it with a phenoxy group. The cyclic phenoxyphosphazene compound may be a compound in which m in the formula (16) represents an integer of 3 to 8.

The chainlike phenoxyphosphazene compound represented by the formula (17) is exemplified by a compound obtained by subjecting hexachloro cyclotriphosphazene, obtained by the above-described method, to ring-opening polymerization at 220 to 250° C., and then substituting thus obtained chainlike dichlorophosphazene having a degree of polymerization of 3 to 10000 with phenoxy groups. The chain-like phenoxyphosphazene compound has a value of n in the formula (17) of 3 to 1000, specifically 5 to 100, and more specifically 6 to 25.

The crosslinked phenoxyphosphazene compound may be exemplified by compounds having a crosslinked structure of a 4,4′-diphenylene group, such as a compound having a crosslinked structure of a 4,4′-sulfonyldiphenylene (bisphenol S residue), a compound having a crosslinked structure of a 2,2-(4,4′-diphenylene)isopropylidene group, a compound having a crosslinked structure of a 4,4′-oxydiphenylene group, and a compound having a crosslinked structure of a 4,4′-thiodiphenylene group. The phenylene group content of the crosslinked phenoxyphosphazene compound is generally 50 to 99.9 wt %, and specifically 70 to 90 wt %, based on the total number of phenyl group and phenylene group contained in the cyclic phosphazene compound represented by the formula (16) and/or the chainlike phenoxyphosphazene compound represented by the formula (17). The crosslinked phenoxyphosphazene compound may be particularly preferable if it doesn't have any free hydroxyl groups in the molecule thereof. In an exemplary embodiment, the phosphazene compound comprises the cyclic phosphazene.

It is desirable for the flame retardant composition to comprise the phosphazene compound in an amount of 1 to 20 wt %, specifically 2 to 15 wt %, and more specifically 2.5 wt % to 10 wt %, based on the total weight of the flame retardant composition.

The flame retardant composition can optionally include impact modifier(s). Suitable impact modifiers are typically high molecular weight elastomeric materials derived from olefins, monovinyl aromatic monomers, acrylic and methacrylic acids and their ester derivatives, as well as conjugated dienes. The polymers formed from conjugated dienes can be fully or partially hydrogenated. The elastomeric materials can be in the form of homopolymers or copolymers, including random, block, radial block, graft, and core-shell copolymers. Combinations of impact modifiers can be used.

A specific type of impact modifier is an elastomer-modified graft copolymer comprising (i) an elastomeric (i.e., rubbery) polymer substrate having a Tg less than 10° C., more specifically less than −10° C., or more specifically −40° to −80° C., and (ii) a rigid polymeric shell grafted to the elastomeric polymer substrate. Materials suitable for use as the elastomeric phase include, for example, conjugated diene rubbers, for example polybutadiene and polyisoprene; copolymers of a conjugated diene with less than 50 wt % of a copolymerizable monomer, for example a monovinylic compound such as styrene, acrylonitrile, n-butyl acrylate, or ethyl acrylate; olefin rubbers such as ethylene propylene copolymers (EPR) or ethylene-propylene-diene monomer rubbers (EPDM); ethylene-vinyl acetate rubbers; silicone rubbers; elastomeric C₁₋₈ alkyl(meth)acrylates; elastomeric copolymers of C₁₋₈ alkyl(meth)acrylates with butadiene and/or styrene; or combinations comprising at least one of the foregoing elastomers. materials suitable for use as the rigid phase include, for example, monovinyl aromatic monomers such as styrene and alpha-methyl styrene, and monovinylic monomers such as acrylonitrile, acrylic acid, methacrylic acid, and the C₁-C₆ esters of acrylic acid and methacrylic acid, specifically methyl methacrylate.

Specific exemplary elastomer-modified graft copolymers include those formed from styrene-butadiene-styrene (SBS), styrene-butadiene rubber (SBR), styrene-ethylene-butadiene-styrene (SEBS), ABS (acrylonitrile-butadiene-styrene), acrylonitrile-ethylene-propylene-diene-styrene (AES), styrene-isoprene-styrene (SIS), methyl methacrylate-butadiene-styrene (MBS), and styrene-acrylonitrile (SAN).

Impact modifiers are generally present in amounts of 1 to 30 wt %, specifically 3 to 20 wt %, based on the total weight of the polymers in the flame retardant composition. An exemplary impact modifier comprises an acrylic polymer in an amount of 2 to 15 wt %, specifically 3 to 12 wt %, based on the total weight of the flame retardant composition.

In an embodiment, the flame retardant composition may comprise an anti-drip agent. Fluorinated polyolefin and/or polytetrafluoroethylene may be used as an anti-drip agent. Anti-drip agents may also be used, for example a fibril forming or non-fibril forming fluoropolymer such as polytetrafluoroethylene (PTFE). The anti-drip agent may be encapsulated by a rigid copolymer such as, for example styrene acrylonitrile (SAN). PTFE encapsulated in SAN is known as TSAN. Encapsulated fluoropolymers may be made by polymerizing the encapsulating polymer in the presence of the fluoropolymer, for example, in an aqueous dispersion. TSAN may provide significant advantages over PTFE, in that TSAN may be more readily dispersed in the composition. A suitable TSAN may comprise, for example, 50 wt % PTFE and 50 wt % SAN, based on the total weight of the encapsulated fluoropolymer. The SAN may comprise, for example, 75 wt % styrene and 25 wt % acrylonitrile based on the total weight of the copolymer. Alternatively, the fluoropolymer may be pre-blended in some manner with a second polymer, such as for, example, an aromatic polycarbonate resin or SAN to form an agglomerated material for use as an anti-drip agent. Either method may be used to produce an encapsulated fluoropolymer.

The anti-drip agent may be added in the form of relatively large particles having a number average particle size of 0.3 to 0.7 mm, specifically 0.4 to 0.6 millimeters. The anti-drip agent may be used in amounts of 0.01 wt % to 5.0 wt %, based on the total weight of the flame retardant composition.

The flame retardant composition may also comprise mineral fillers. In an embodiment, the mineral fillers serve as synergists. In an embodiment, a small portion of the mineral filler may be added to the flame retardant composition in addition to a synergist, which can be another mineral filler. The synergist facilitates an improvement in the flame retardant properties when added to the flame retardant composition over a comparative composition that contains all of the same ingredients in the same quantities except for the synergist. Examples of mineral fillers are mica, talc, calcium carbonate, dolomite, wollastonite, barium sulfate, silica, kaolin, feldspar, barites, or the like, or a combination comprising at least one of the foregoing mineral fillers. The mineral filler may have an average particle size of 0.1 to 20 micrometers, specifically 0.5 to 10 micrometers, and more specifically 1 to 3 micrometers.

The mineral filler is present in amounts of 0.1 to 20 wt %, specifically 0.5 to 15 wt %, and more specifically 1 to 5 wt %, based on the total weight of the flame retardant polycarbonate composition. An exemplary mineral filler is talc having a particle size of 1 to 3 micrometers.

In an embodiment, the flame retardant composition may contain a silicone oil. The silicone oil a high viscosity silicone containing a combination of a linear silicone fluid, and a silicone resin that is solubilized in the fluid.

The silicone oil is present in an amount of 0.5 to 10 wt %, specifically 1 to 5 wt %, based on the total weight of the flame retardant composition. In an embodiment, the silicone oil comprises a polysiloxane polymer endcapped with trimethylsilane; where the silicone oil has a viscosity at 25° C. of 20,000 to 900,000 square millimeter per second. A commercially available silicone oil for use in the flame retardant composition is SFR®-100 commercially available from Momentive.

In an embodiment, the flame retardant composition may optionally comprise other flame retardants in addition to or instead of the phenoxyphosphazene compounds. These additional flame retardants may be bisphenol A diphosphate, resorcinol diphosphate, brominated polycarbonate, Rimar salt (potassium perfluorobutane sulfonate) KSS (potassium diphenylsulfone sulfonated, and the like. These additional flame retardants may be used in amounts of 0.5 to 10 wt %, specifically 1 to 5 wt %, based on the total weight of the flame retardant composition.

Other additives such as anti-oxidants, anti-ozonants, mold release agents, thermal stabilizers, levelers, viscosity modifying agents, free-radical quenching agents, other polymers or copolymers such as impact modifiers, or the like.

The preparation of the flame-retardant composition can be achieved by blending the ingredients under conditions that produce an intimate blend. All of the ingredients can be added initially to the processing system, or else certain additives can be precompounded with one or more of the primary components.

In an embodiment, the flame-retardant composition is manufactured by blending the polycarbonate copolymer with the phosphazene compound. The blending can be dry blending, melt blending, solution blending, or a combination comprising at least one of the foregoing forms of blending.

In an embodiment, the flame-retardant composition can be dry blended to form a mixture in a device such as a Henschel mixer or a Waring blender prior to being fed to an extruder, where the mixture is melt blended. In another embodiment, a portion of the polycarbonate copolymer can be premixed with the phosphazene compound to form a dry preblend. The dry preblend is then melt blended with the remainder of the polyamide composition in an extruder. In an embodiment, some of the flame retardant composition can be fed initially at the mouth of the extruder while the remaining portion of the flame retardant composition is fed through a port downstream of the mouth.

Blending of the flame retardant composition involves the use of shear force, extensional force, compressive force, ultrasonic energy, electromagnetic energy, thermal energy or combinations comprising at least one of the foregoing forces or forms of energy and is conducted in processing equipment wherein the aforementioned forces are exerted by a single screw, multiple screws, intermeshing co-rotating or counter rotating screws, non-intermeshing co-rotating or counter rotating screws, reciprocating screws, screws with pins, barrels with pins, rolls, rams, helical rotors, or combinations comprising at least one of the foregoing.

Blending involving the aforementioned forces may be conducted in machines such as single or multiple screw extruders, Buss kneader, Henschel, helicones, Ross mixer, Banbury, roll mills, molding machines such as injection molding machines, vacuum forming machines, blow molding machine, or then like, or combinations comprising at least one of the foregoing machines.

The flame-retardant composition can be introduced into the melt blending device in the form of a masterbatch. In such a process, the masterbatch may be introduced into the blending device downstream of the point where the remainder of the flame retardant composition is introduced.

In an embodiment, the flame-retardant composition disclosed herein are used to prepare molded articles such as for example, durable articles, electrical and electronic components, automotive parts, and the like. The compositions can be converted to articles using common thermoplastic processes such as film and sheet extrusion, injection molding, gas-assisted injection molding, extrusion molding, compression molding and blow molding.

In an embodiment, the flame retardant compositions when prepared into test specimens having a thickness of at least 1.2 mm, exhibit a flammability class rating according to Underwriters Laboratories Inc. UL-94 of at least V-2, more specifically at least V-1, and yet more specifically at least V-0. In another embodiment, the flame retardant compositions when prepared into specimens having a thickness of at least 2.0 millimeters, exhibit a flammability class rating according to Underwriters Laboratories Inc. UL-94 of at least V-2, more specifically at least V-1, and yet more specifically at least V-0.

Flammability tests were performed following the procedure of Underwriter's Laboratory Bulletin 94 entitled “Tests for Flammability of Plastic Materials, UL 94.” Several ratings can be applied based on the rate of burning, time to extinguish, ability to resist dripping, and whether or not drips are burning. Samples for testing are bars having dimensions of 125 mm length×13 mm width by no greater than 13 mm thickness. Bar thicknesses were 0.6 mm or 0.8 mm. Materials can be classified according to this procedure as UL 94 HB (horizontal burn), V0, V1, V2, 5VA and/or 5VB on the basis of the test results obtained for five samples; however, the compositions herein were tested and classified only as V0, V1, and V2, the criteria for each of which are described below.

V0: In a sample placed so that its long axis is 180 degrees to the flame, the period of flaming and/or smoldering after removing the igniting flame does not exceed ten (10) seconds and the vertically placed sample produces no drips of burning particles that ignite absorbent cotton. Five bar flame out time is the flame out time for five bars, each lit twice, in which the sum of time to flame out for the first (t1) and second (t2) ignitions is less than or equal to a maximum flame out time (t1+t2) of 50 seconds.

V1: In a sample placed so that its long axis is 180 degrees to the flame, the period of flaming and/or smoldering after removing the igniting flame does not exceed thirty (30) seconds and the vertically placed sample produces no drips of burning particles that ignite absorbent cotton. Five bar flame out time is the flame out time for five bars, each lit twice, in which the sum of time to flame out for the first (t1) and second (t2) ignitions is less than or equal to a maximum flame out time (t1+t2) of 250 seconds.

V2: In a sample placed so that its long axis is 180 degrees to the flame, the average period of flaming and/or smoldering after removing the igniting flame does not exceed thirty (30) seconds, but the vertically placed samples produce drips of burning particles that ignite cotton. Five bar flame out time is the flame out time for five bars, each lit twice, in which the sum of time to flame out for the first (t1) and second (t2) ignitions is less than or equal to a maximum flame out time (t1+t2) of 250 seconds.

In an embodiment, the flame retardant compositions are of particular utility in the manufacture flame retardant articles that pass the UL94 vertical burn tests, in particular the UL94 5VB standard. In the UL94 vertical burn test, a flame is applied to a vertically fastened test specimen placed above a cotton wool pad. To achieve a rating of 5VB, burning must stop within 60 seconds after five applications of a flame to a test bar, and there can be no drips that ignite the pad.

If a sample can pass 5VB, then the sample can continue to be tested on 5VA to get a 5VA listing. Various embodiments of the compositions described on 5VA meet the UL94 5VB standard. The test is conducted as follows:

Support the plaque specimen (150±5 mm×150±5 mm) by a clamp on the ring stand in the horizontal plane. The flame is then to be applied to the center of the bottom surface of the plaque at an angle of 20±5° from the vertical, so that the tip of the blue cone just touches the specimen. Apply the flame for 5±0.5 seconds and then remove for 5±0.5 seconds. Repeat the operation until the plaque specimen has been subjected to five applications of the test flame. When desired, to complete the test, hand hold the burner and fixture so that the tip of the inner blue cone maintains contact with the surface of the plaque. After the fifth application of the test flame, and after all flaming or glowing combustion has ceased, it is to be observed and recorded whether or not the flame penetrated (burned through) the plaque.

A VXTOOL test is used to estimate p(FTP), i.e., the probability for a first time pass when subjected to a flame. In the VXTOOL test, 20 flame bars are burnt as per UL94 test protocols and the flame data is analyzed to estimate the p(FTP) values. The p(FTP) value can range between 0 and 1 and indicates the probability that the first five bars when tested for V-0 or V-1 UL94 test would pass. A higher p(FTP) value indicates the greater likelihood of passing and therefore an improved flame retardancy. Thus, a VXTOOL p(FTP)V-0 of 1.0 signifies a very high confidence/probability of attaining the V-0 flame rating, whereas a p(FTP)V-0 of 0.0 indicates a very poor probability of attaining the V-0 flame rating.

Izod Impact Strength is used to compare the impact resistances of plastic materials. Notched Izod impact strength was determined at both 23° C. and 0° C. using a 3.2-mm thick, molded, notched Izod impact bar. It was determined per ASTM D256. The results are reported in Joules per meter. Tests were conducted at room temperature (23° C.) and at a low temperature (−20° C.).

Heat deflection temperature (HDT) is a relative measure of a material's ability to perform for a short time at elevated temperatures while supporting a load. The test measures the effect of temperature on stiffness: a standard test specimen is given a defined surface stress and the temperature is raised at a uniform rate. HDT was determined as flatwise under 1.82 MPa loading with 3.2 mm thickness bar according to ASTM D648. Results are reported in ° C.

Melt volume rate (MVR) is measured 300° C./1.2 kg as per ASTM D 1238.

The flame retardant composition displays an advantageous combination of properties such as ductility, melt processability, impact strength, and flame retardancy.

The following examples, which are meant to be exemplary, not limiting, illustrate the flame retardant compositions and methods of manufacturing of some of the various embodiments of the flame retardant compositions described herein.

EXAMPLE

The following examples were conducted to demonstrate the disclosed composition and the method of manufacturing a flame retardant polycarbonate composition that comprises a polycarbonate homopolymer, a polysiloxane-polycarbonate copolymer and a phosphazene oligomer. The polycarbonate used in the homopolymer or in the various copolymers may be a linear polymer or a branched polymer. This example was conducted to demonstrate that the phosphazene compounds can be used in the polycarbonate compositions and can produce flame retardant compositions that display flame retardancy without losing ductility or impact resistance.

This example details the use of a polysiloxane-polycarbonate copolymer blended with a linear polycarbonate. The polycarbonate composition therefore comprises a linear polycarbonate in addition to a polysiloxane-polycarbonate copolymer. The polysiloxane-polycarbonate copolymer acts synergistically with the phosphazene compound to produce ductile transparent flame retardant compositions that display UL94 V-0 at 1.0 mm sample thicknesses. In the Table 1, Sample #1 contains BPADP which is a comparative flame retardant. Sample #1 is therefore a comparative composition, while Sample #s 2 and 3 contain the phosphazene compounds.

Table 1 lists ingredients used in the following examples along with a brief description of these ingredients. Table 2 lists the compounding conditions and Table 3 lists molding conditions.

TABLE 1 Ingredient Description BPA-Polycarbonate Bisphenol A polycarbonate—linear having a weight average molecular weight between 22,000 and 30,000 grams per mole. Polysiloxane- Opaque polysiloxane-polycarbonate copolymer polycarbonate having 20 wt % polysiloxane with a copolymer molecular weight of 33,000 grams per mole. Pentaerythritol Mold release agent tetrastearate Phosphite stabilizer Thermal stabilization additive SPB-100 Flame retardant compound phosphazene BPADP Bisphenol A diphosphate (flame retardant) T-SAN Flame retardant anti-drip agent Fine Talc Flame retardant synergist

The compounding was conducted on a Toshiba SE37 mm twin-screw extruder having 11 barrels. The temperature for each of the barrels is detailed in the Table 2. All the components were fed from the main throat of the extruder. The additives (phosphazene, stabilizers, mold release agents) were pre-blended with the polycarbonate powder in a super blender and then fed into the extruder via the main throat.

TABLE 2 Extruder Type Unit of Measure TEM-37BS Barrel Size mm 1500 Screw Design NONE L-3-1B Die mm 3 Zone 1 Temp ° C. 50 Zone 2 Temp ° C. 100 Zone 3 Temp ° C. 270 Zone 4 Temp ° C. 270 Zone 5 Temp ° C. 270 Zone 6 Temp ° C. 270 Zone 7 Temp ° C. 270 Zone 8 Temp ° C. 270 Zone 9 Temp ° C. 270 Zone 10 Temp ° C. 270 Zone 11 Temp ° C. 270 Die Temp ° C. 270 Screw speed rpm 400 Throughput kg/hr 40 Torque % 77 Vacuum 1 MPa −0.08 Side Feeder 1 speed rpm 250

Extruded pellets were dried in a dehumidifying dryer for 4 hours at 90° C. Different thickness of UL94 testing bars, i.e. 1.0 mm, 1.2 mm, 2.0 mm and 2.5 mm were molded with single gate tooling, and 0.3 mm, 0.4 mm were molded with film gate tooling. Table 3 shows the molding condition.

TABLE 3 Pre-drying time Hour 4 Pre-drying temp ° C. 90 Hopper temp ° C. 50 Zone 1 temp ° C. 255 Zone 2 temp ° C. 260 Zone 3 temp ° C. 260 Nozzle temp ° C. 260 Mold temp ° C. 40 Screw speed rpm 100 Back pressure kgf/cm² 40 Molding Machine NONE Nestal Mold Type NONE UL 0.3 and (insert) 0.4 mm film gate Injection mm/s 300 speed(mm/s) Holding pressure kgf/cm² 2400 Max. Injection kgf/cm² 2800 pressure Transfer pressure kgf/cm² 2800

Properties of the thermoplastic compositions were determined herein as follows. Molecular weight of polymers (Mn, Mw, and polydispersity) was determined by using gel permeation chromatography (GPC). Notched Izod impact (NII) were determined according to ASTM D256. MVR and MFR were determined at 300° C. under load of 1.2 kg according to ASTM D1238. Heat deflection temperature (HDT) (° C.) was determined as flatwise under 1.8 MPa loading with 3.2 mm thickness bar according to ASTM D648. Glass transition temperature (Tg) is measured by Differential Scanning calorimeter (DSC). Transmission (T %) and Haze (%) were both measured by Haze-Guard II per ASTM D1003. UL94 Vx Testing is per UL protocol as the following procedure: Flame bars were conditioned for 48 hours at 23° C. and 50% relative humidity as regular aging, as well as for 168 hours at 70° C. for heat aging respectively. The bars were burnt at the gated end for Vx evaluation. For some specific examples only 5 flame bars were tested and a footnote was mark as such. For majority of examples 10 flame bars were tested.

The flame performance has been observed through the following parameters:

-   -   (i) FOT—average flame-out time of first (time₁) and second         (time₂) (in footnoted case, within 5 bars)     -   (ii) Burn out—the number of long-flame-out within 10 flame bars         (in footnoted case, within 5 bars)     -   (iii) Drip—the number of drips within 10 flame bars (in         footnoted case, within 5 bars)     -   (iv) p(FTP)— probability of pass     -   (v) Rating—Fail, V-2, V-1 or V0     -   (vi) In some examples, details time1/times flame-out time were         listed to demonstrate robust flame retardant performance.

The p(FTP) values include the FOTs and the burning characteristics to estimate the probability that the first five or ten bars will pass the specified rating if tested under UL94 protocols. Thus p(FTP) ranges between 0 and 1, with higher values (values closer to 1) indicating a higher likelihood of passing a particular rating.

The compositions along with the properties are shown in the Table 4. As shown in Table 4, linear bisphenol A polycarbonate is blended with 8 or 12 wt % of the phosphazene (SPB-100) (Sample #s 2 and 3) respectively or alternatively with the BPADP (Sample #1). The compositions contain TSAN and talc, which functions as a synergist.

As can be seen in the Table 4, the use of phosphazene compounds can improve the heat distortion temperature (HDT) of polycarbonate, while has no obvious effect on molecular weight reduction. The use of a polysiloxane-polycarbonate copolymer having a molecular weight greater than 30,000 grams per mole and where the weight percentage of the polysiloxane in the polysiloxane-polycarbonate copolymer is greater than 10 wt %, specifically greater than or equal to 12 wt %, specifically greater than or equal to 16 wt %, and more specifically greater than or equal to 18 wt %, produces a flame retardant composition that displays a flame retardancy of V-0 at a thickness of 0.3 millimeter, while at the same time displaying a notched Izod impact of greater than 950 joules per meter.

The examples in the Table 4 below show flame performance along with other properties for flame retardant compositions comprising linear polycarbonates, opaque polysiloxane-polycarbonate polymers along with a phosphazene compound.

TABLE 4 Item Description Unit #1 #2 #3 Formula BPA-Polycarbonate wt % 73.625 77.625 73.625 TSAN wt % 0.2 0.2 0.2 Pentaerythritol tetrastearate wt % 0.13 0.13 0.13 Phosphite stabilizer wt % 0.045 0.045 0.045 Fine Talc wt % 4 4 4 BPADP wt % 12 SPB-100 wt % 8 12 Opaque polysiloxane-carbonate wt % 10 10 10 copolymer Properties MVR cm³/10^(min) 9.75 13.5 14 Notched IZOD impact J/m 76.1 1010 1030 HDT ° C. 92.4 108 99 Mw Daltons 68473 61819 62991 Mn Daltons 28991 25424 25804 D = Mw/Mn — 2.36 2.43 2.44 VX 0.3 mm 23° C./48 h FOT s 39.35 18.6 Drip 1 0 Burn out 3 0 PFTP 0.02 1 Rating V-2 V-0 70° C./168 h FOT s 26.85 19.35 Drip 0 0 Burn out 2 0 PFTP 0.2 0.99 Rating V-2 V-0 VX 0.4 mm 23° C.*48 h FOT s 32.7 24.45 24.05 Burn out 1 0 0 Drip 1 0 0 PFTP 0.47 0.93 0.99 Rating V-2 V-0 V-0 70° C./168 h FOT s 21.95 24.6 17.45 Burn out 0 0 0 Drip 0 0 0 PFTP 0.96 0.99 1 Rating V-0 V-0 V-0

As can be seen in the Table 4, the use of phosphazene compounds can improve the heat distortion temperature (HDT) of polycarbonate, while has no obvious effect on molecular weight reduction. The use of a polysiloxane-polycarbonate copolymer having a molecular weight greater than 30,000 grams per mole, where the weight percentage of the polysiloxane in the polysiloxane-polycarbonate copolymer is greater than 10 wt %, specifically greater than or equal to 12 wt %, specifically greater than or equal to 16 wt %, and more specifically greater than or equal to 18 wt %, produces a flame retardant composition that displays a flame retardancy of V-0 at a thickness of 0.3 millimeter, while at the same time displaying a notched Izod impact of greater than 950 joules per meter, specifically greater than or equal to 1000 joules per meter.

From the Table 4 it may be seen that Sample #29 which contains the BPADP (the comparative flame retardant), while formulation with SPB-100 gives the robust FR performance at 0.3 and 0.4 mm, and UL94 V-0 can be listed at 0.3 mm. It should be noted that sample #29 in Table 10 is brittle, while a ductile material can be achieved when SPB-100 is used in conjunction with the polysiloxane-polycarbonate copolymer. From the Table 4, it can be seen that the notched Izod impact strength of the sample #31 is greater than 1000 J/m. A ductile sample displaying a flame retardancy of UL94 V-0 at 0.3 mm cannot be manufactured by using only BPADP and the polycarbonate-polysiloxane copolymer, can be achieved by using SPB-100 in conjunction with polycarbonate-polysiloxane.

As shown in Table 4, when a polysiloxane-polycarbonate copolymer having 10 wt % or more of the polysiloxane and a molecular weight of greater than 30,000 Daltons was used the flame retardant composition a robust UL94 V-0 rating at 0.4 mm sample thickness can be achieved. From the Table 4 it can also be seen that when talc is used in the flame retardant composition in conjunction with phosphazene, polysiloxane-polycarbonate copolymer, linear polycarbonate, and TSAN a UL94 V-0 at 0.3 mm thickness can be obtained.

As may be seen in the example above, the flame retardant composition has a flame retardancy of V-0, V-1, or V-2, at various thicknesses when tested according to the UL-94 protocol. The sample thickness can be 0.1 millimeter or less, 0.3 millimeter or less, specifically 0.4 millimeter or less, specifically 0.8 millimeter or less, specifically 1.0 mm or less, specifically 1.2 mm or less, specifically 1.5 mm or less, specifically 1.8 mm or less, specifically 2.0 mm or less, specifically 3.0 mm or less.

In another embodiment, the flame retardant composition may be opaque and can have a flame retardancy of V-0, V-1 or V-2, at various thicknesses when tested according to the UL94 protocol. The sample thickness can be 0.3 millimeter or greater, specifically 0.4 millimeter or greater, specifically 0.8 millimeter or greater, specifically 1.0 mm or greater, specifically 1.2 mm or greater, specifically 1.5 mm or greater, specifically 1.8 mm or greater, specifically 2.0 mm or greater, when tested according to the UL94 protocol. At all of these thicknesses the flame retardant composition can display a flame retardancy of V-0, V-1, or V-2 depending the selected composition.

In summary, in an embodiment, the flame retardant composition comprises a linear polycarbonate; a polysiloxane-polycarbonate copolymer; and a phosphazene compound. The flame retardant composition is optically transparent when measured as per ASTM D 1003. In an embodiment, the flame retardant composition has an optical transparency greater than 75%, specifically greater than 95% when measured as per ASTM D 1003.

In an embodiment, the composition comprises an antidrip agent. The flame retardant composition has a flame retardancy of V-0 at a thickness of 1.5 millimeter or lower, specifically 1.2 millimeter or lower, specifically 0.8 millimeter or lower, specifically 0.4 millimeter or lower, and more specifically 0.3 millimeter or lower, when measured as per a UL-94 protocol. In an embodiment, the flame retardant composition does composition does not contain a flame retardant other than the phosphazene compound.

While the invention has been described with reference to some embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

What is claimed is:
 1. A flame retardant composition comprising: 10 to 90 weight percent of a linear polycarbonate; 5 to 50 weight percent of a polysiloxane-polycarbonate copolymer; where the polysiloxane-polycarbonate copolymer comprises 10 weight percent or more of polysiloxane and where the molecular weight of the polysiloxane is 30,000 grams per mole or greater; and 1 to 20 weight percent of a phosphazene compound; where all weight percents are based on the total weight of the composition.
 2. The composition of claim 1, where the linear polycarbonate is derived from bisphenol A polycarbonate and where the linear polycarbonate has a weight average molecular weight of 15,000 to 60,000 Daltons as determined by a polycarbonate standard.
 3. The composition of claim 2, where the linear polycarbonate is derived from a blend of two linear polycarbonate homopolymers, where one linear polycarbonate homopolymer has a higher molecular weight that the other linear polycarbonate homopolymer.
 4. The composition of claim 1, where the phosphazene compound is present in an amount of 3 to 10 wt %, based on a total weight of the flame retardant composition.
 5. The composition of claim 1, where the phosphazene compound has the structure of formula (16)

wherein the formula (16), m represents an integer of 3 to 25, and where R₁ and R₂ are the same or different and are independently a hydrogen, a hydroxyl, a C₁₋₁₂ alkoxy, or a C₁₋₁₂ alkyl.
 6. The composition of claim 1, where the phosphazene compound is phenoxy cyclotriphosphazene, octaphenoxy cyclotetraphosphazene, decaphenoxy cyclopentaphosphazene, or a combination comprising at least one of the foregoing phosphazene compounds.
 7. The composition of claim 1, where the phosphazene compound has the structure of formula (17)

where in the formula (17), X¹ represents a —N═P(OPh)₃ group or a —N═P(O)OPh group, Y¹ represents a —P(OPh)₄ group or a —P(O) (OPh)₂ group, n represents an integer from 3 to 10000, Ph represents a phenyl group, R1 and R2 are the same or different and are independently a hydrogen, a hydroxyl, a C₁₋₁₂ alkoxy, or a C₁₋₁₂ alkyl.
 8. The composition of claim 1, where the phosphazene compound is a crosslinked phenoxyphosphazene.
 9. The composition of claim 1, where the phenoxyphosphazene compound has a structure represented by the formula (19)

where R1 to R6 can be the same of different and can be an aryl group, an aralkyl group, a C₁₋₁₂ alkoxy, a C₁₋₁₂ alkyl, or a combination thereof.
 10. The composition of claim 1, where the phenoxyphosphazene compound has a structure represented by the formula (20)


11. The composition of claim 1, where the polysiloxane-polycarbonate copolymer has the structure shown in the Formula (15) below:

where x is 30 to 50, y is 10 to 30 and z is 450 to
 600. 12. The composition of claim 15, further comprising an antidrip agent, talc or a combination thereof.
 13. The composition of claim 1, where the composition has a flame retardancy of V-0 at a thickness of 0.3 millimeter or lower when measured as per a UL-94 protocol.
 14. The composition of claim 1, where the composition has a flame retardancy of V-0 at a thickness of 0.4 millimeter or lower when measured as per a UL-94 protocol.
 15. The composition of claim 1, where the composition has a flame retardancy of V-0 at a thickness of 0.8 millimeter or lower when measured as per a UL-94 protocol.
 16. The composition of claim 1, where the composition has a flame retardancy of V-0 at a thickness of 1.2 millimeter or lower when measured as per a UL-94 protocol.
 17. The composition any one of claims 1, where the composition has a flame retardancy of V-0 at a thickness of 1.5 millimeter or lower when measured as per a UL-94 protocol.
 18. The composition any one of claims 1, where the composition does not contain a flame retardant other than the phosphazene compound.
 19. A method comprising: blending 10 to 90 weight percent of a linear polycarbonate; 5 to 50 weight percent of a polysiloxane-polycarbonate copolymer; where the polysiloxane-polycarbonate copolymer comprises 10 weight percent or more of polysiloxane and where the molecular weight of the polysiloxane is 30,000 grams per mole or greater; and 1 to 20 weight percent of a phosphazene compound; where all weight percents are based on the total weight of the composition; to form a flame retardant composition; were all weight percents are based on the total weight of the composition.
 20. The method of claim 19, where the blending is conducted in an extruder.
 21. The method of claim 19, further comprising injection molding the flame retardant composition.
 22. An article manufactured from the composition of claim
 1. 